The first strong evidence that a specific gene causes some prostate cancer cases was announced Thursday by an international research team.
The gene, not yet isolated, resides on human chromosome 1 and seems responsible for about 5 percent of prostate tumors, especially those that occur at relatively young ages (men in their 50s), the researchers said.
Cancer of the prostate gland is the most common malignancy seen in American males, with 317,000 new cases and about 41,000 deaths reported annually, according to American Cancer Society figures.
“This is a very significant development,” said Dr. Francis Collins, director of the Human Genome Project at the National Institutes of Health in Bethesda, Md. “Because early detection is the way to survive, this could potentially play a very useful role” in identifying men at risk and treating tumors early.
The gene’s existence was detected by studying the disease’s inheritance patterns in 91 families. By using molecular techniques to determine who inherited which chromosomes, scientists narrowed the search to a small portion of chromosome 1. No other cancer gene is known to reside close to that part of the human set of genes, Collins said.
Based on these family studies, the researchers think as many as 10 percent of prostate-cancer cases are inherited, and that the gene may account for half of those. According to Collins, there may be one, two or more such genes involved in familial prostate cancer.
Dr. Bruce Zetter, who specializes in studying the rapid spread of malignant cells from the prostate gland, said the discovery is important because “it can lead us toward a mechanism for the formation of prostate tumors.”
And, he said, “for this population, who are going to get more serious tumors at a younger age, it will be very helpful to have them designated so they can get earlier screening and have better follow-up.” Zetter, who was not involved in the project, does his research at Children’s Hospital in Boston.
Collins noted that the patterns seen with the prostate-cancer gene are reminiscent of what is seen for inherited breast cancer. So far, two tumor-suppressor genes - BRCA-1 and BRCA-2 - account for almost 10 percent of breastcancer cases. The two BRCA genes also raise the risk of ovarian cancer and seem to be weakly associated with prostate cancer.
“It is sort of eerie in terms of the similarities” between the new prostate-cancer gene and the breast-cancer genes, Collins said. The two breast-cancer genes have been isolated and are being studied. In fact, diagnostic tests are in use to determine which patients are at high risk for breast and ovarian cancer.
Collins said the key development in the search for a prostate-cancer gene came from Dr. Patrick Walsh, a urologic surgeon at the Johns Hopkins Medical Institutions in Baltimore. Walsh focused on men who developed prostate cancer early, in their 50s.
“If you look at early onset, the fraction (of cases) attributable to heredity is much higher, just as with breast cancer,” Collins explained. Looking at early-onset cases and their families allowed Walsh and his colleagues to find and follow the 91 families with an inherited susceptibility.
The 23-member team reported the new findings in Science magazine.